Forge Welding Temps?? pics added, more to come

Sorry Chuck When I posted I was thinking you where doing a single weld heat on your 9 layer billet and trying to compare the two billets.
 
I've had the same issue to a lesser extent over the years Chuck. I believe you're on the right track with the temperature difference. As for the mechanism that makes it muddy at higher layer counts, I'm not sure, but I have a few ideas. It could be diffusion of some alloying elements, but when you're sticking with simple steels like 1084/15n20 there's not much to diffuse from one to the other, and I doubt that the nickel is really going to go much of anywhere. My gut tells me that lots forging/deformation at the higher temps may be the culprit. To my way of thinking, higher temps mean more a more plastic state for the steels involved, and higher layer counts means thinner layers. Add these two together and it becomes much easier to push one layer THROUGH an adjacent layer a bit if there is a thicker section to one of the layers (and at higher layer counts those layers can be VERY thin, so it wouldn't take much). The other option for the action would be like trying to roll out a kind of dry clay or dough too thin, or too quickly. It would crack and separate a bit at the edges. Now, picture that at the interface between two very thin layers and you can get the "fuzzy" effect you see at the layer interfaces. Not that anything is coming apart per se, but just shifting around at the edges.

I wonder what would happen if you took your welding heats at your normal 2300F or so and then ran your subsequent forging more slowly and at 1900-2000. Then, try reversing that and welding at 1900 or so and then forging hot to see what the difference would be.

-d
 
The following is one possible explanation:

One thing that often escapes these discussions is that diffusion and "melding" are a process of time and temperature. Long heats and many cycles of them may cause some problems like you have found. This will only account for part of the problem, as temperature is the far greater factor. If steel is heated to ( fictitious numbers for point of explanation) 2400°F it may not start to meld...... However at 2500°F it may. There is a second factor of heat that we often forget about, but is a critical part of welding.....Force ( pressure). The force applied by the hammer/press adds energy to the layers and the heat rises at the point of contact. This can locally take 2400°F steel and raise it to 2500°F or more in a milli-second. We all remember hearing about the smith who would hit some cold steel so fast and hard that he gets it glowing ( not sure about that story, but the principle is correct). In forge welding, the same principal applies. If using a large hammer or press, you may fuse some layers more than others, because these localized areas reach a higher temperature under the higher force. This could cause some "muddy" areas.
 
Well I still think Chuck the fuzzy muddy looking blade billet was to hot to long.

I would like to see you make a billet for 2000º and a billet for each +100º up to 2500º all the same layer count but just forge each one at the appropriate temp and be careful to do the same amount of heat cycles and time at temps soaks. Then forge a blade from teach billet at 2000º or below and lets see how they look. Maybe you could find someone with a microscope that could take some pictures to see what is going on close up.
 
I agree with Mike on this. The temperature seems to have the largest affect on the appearance of the billet. Time is important, but its affect can be greatly minimized at a lower temp.

Steven, if you come down for a class we can talk about the digi camp blade.
 
A dry weld is when you use a box or weld up the seams on your billet to prevent oxidation. This removes the requirements for the use of a flux.
 
Grain boundaries are always more active. So they oxidize more easily and they melt more easily when you get a too high temperature !! I would assume it's the melting grain boundaries that causes the problem.
 
A little off topic maybe, but how are you normalizing and annealing? I had something like this happen a few years ago with chain damascus. Pretty sure it was the extra long soak I did. I haven't had this problem anymore recently, but that could be that as soon as the billet is up to temp I weld it, and most times I give it a quick normalize after drawing out to be cut for re-stacking. Then I give the finished blade multiple normalizing cycles. I forge to shape at welding temp also, but the last couple of heats are in the forging range, and a final "edge packing" heat. I know "edge packing" doesn't exist, it's the last low heat forging I do, not much metal being move, just a little fine tweaking and smoothing everything up, then to normalizing. I guess you could call "edge packing" a normalizing forging heat?

Then again maybe the reason I haven't had this issue lately is that I use 1084 and 15&20, haven't used 1095 in a LONG time. Might have something to do with it?

In any event, just some thoughts, and I'm interested in seeing others thoughts on the subject.
 
I know this is old Chuck.

I'm forge welding wet and dry at around 2100-2200. Once welded, I keep temps well under 2000, 1600-1900 is a good forging range for me. I've also done dry welds below 2000 with very good results. Years ago I watched Darrel Meyer do a dry weld at around 1200. ;)

I also agree 1080-1084/15n20 is a 'better looking' mix. I stopped using 1095 a long time ago.
 
Don

I had heard about the 1200 dry weld but could not remember who did it. Glad you witnessed it and could confirm who it was. BTW some of your previous posts had prompted this testing. It has made a big difference in the quality of my billets.

Will

I have not done a normalizing between welds. I do know that that the more a billet is worked the shadows go away. The problem arises with a tiled mosaic. You cannot work them as much after final weld-up as there is a risk of pattern distortion. The dry welding process has eliminated the need for that extra low temp forging.
 
Mete,

I agree fully. I have had a different situation arise when I do not have perfect mating surfaces and a small gap is present. The gap seems to fill with melted material and cause a pattern interruption. Very distracting in a fine active pattern. Another reason I take the extra time to ensure a perfect weld.
 
AC--If you remember, we talked using PM's on this subject a while back, focusing on welding temperatures. I said that since I switched to dry welding exclusively my welding temperatures have dropped by 100 degrees plus. 2350 to 2250. I get cleaner and better welds with this process. I have noticed that with random pattern welds where all the steel is stacked using individual layers; each piece that makes up the billet are identical by length and width, I am getting much more distinct patterns when ground and etched.
Do you think, when working at the higher temperatures with random pattern billets, that the heat is affecting the layers "more" during the weld than a billet, like a feather pattern, with its pieces running in multiple directions.
When I make up a random pattern billet using thinner 15n20 I weld the billet down both sides in order to hold the thinner pieces in place while it comes to welding temp as well as during the actual welding process. I know I could see the thinner material in a random pattern billet move while it was coming to temperature before I began welding down the sides. After the first weld there is no need to weld the sides because thicker pieces make up the billet.
I read back over this and don't know if I am making seance or not. I'll check back and see if there is any comment on this.
Have a good one, Fred
 
Don Nguyen said:
How in the world does a weld at 1200 work?
Click to expand...

When I saw Darrel Meyer do it, the pieces were very flat and at a 220 grit finish. He also pointed out, if enough pressure was applied, no heat at all wold be needed. :cool:

This demo was just to show what can be done, he still recommend more heat be used.

I have made very nice, clean welds at around 1800.

Much over 2100-2200 my damascus starts looking kind of nasty...
 
Just wanted to add my limited 2c, I don't have aa thermocouple in my welding forge, and I weld pretty hot, definitely high bright yellow on some big stacks, and I haven't had too much problem with definition on 200ish layer randoms or other patterns where you're pulling the pattern up through the layers, but I have never forged my blades out from the billet above normal forging temps.

I would be very concerned about overheating in thinner cross sections. I usually take them down to half or quarter inch, then either surface grind, or forge directly to dimensions from there at the same temps as mono steel.

I use 15n20/1084 exclusively, and won't normally anneal but will do the appropriate thermal cycling regime. I've also noticed this usually takes care of any silver lines from wet weld imperfections, especially by the time I finish HT.

My experience is limited, only been making damascus for a couple of years, so take that for what you will.

Here's a pic of a recent 200 layer billet, that I ground some diamonds into with the angle grinder after the last weld, then drew out, surface ground it lightly, then forged at normal temps.

20120611_063421.jpg


So from my limited knowledge, heat definitely seems the culprit, but I'm not sure it's the welding temps so much as the forging temps.

When I draw out billets to cut and restack, especially if I'm drawing under half an inch thick, I dont heat them beyond usual hot forging temps, a high orange, low yellow.
 
Don Hanson III said:
He also pointed out, if enough pressure was applied, no heat at all wold be needed. :cool:

This demo was just to show what can be done, he still recommend more heat be used.

.
Click to expand...
There is a process used in the clad plate industry that uses nothing but pressure to weld..The two plates are placed together with explosive on the top..The pressure from the explosion welds them together.
We have a couple pieces setting against the shop..Didnt know what it was until Phillip tried to cut it with a torch..
 
Yes it can be done with pressure alone. Explosive welding is actually pretty common. Though it is not easily done by the home/small shop maker. One can send it out and have a batch done. It works with dissimilar metals also, ie aluminum and stainless steel.

Fred, All my box's are fully welded and cannot come apart. So the thinner 15n20 cannot heat faster or if it does should not make that much difference due to the lack of O2. The biggest thing I found was that I did not start getting the muddy appearance until I went over the 250 layer count. I was shooting for a 500 layer billet and it came out nasty looking. Since I did this thread I have kept my welding below 2250f. I have not gone as low as Don for day to day work but you cannot argue with his success. My billets are much clearer and more refined.
 
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